New Avon Surgical Technique.qxd 8/5/03 12:14 PM Page 2 · Introduction Isolated patello-femoral arthritis occurs in up to 10% of patients with arthritic symptoms in the knee joint.1,2,3

New Avon Surgical Technique.qxd 8/5/03 12:14 PM Page 2

IntroductionIsolated patello-femoral arthritis occurs in up to 10% of patients with arthritic symptoms in the knee joint.1,2,3 Conservative treatment is

reasonably effective in improving the symptoms, but eventually when the articular cartilage has completely eroded, the symptoms may become

intrusive.Typically, there is swelling and giving way of the joint, difficulties with steps and stairs and negotiating hills increases the severity of the

symptoms.

In the past a patellectomy has been a common treatment which leaves the knee joint significantly weakened and the clinical results are excellent

in less than 50% of cases .4

Development of the total knee replacement has shown that the patello-femoral joint can be successfully replaced. Modern joint replacements,

where the biomechanics of the patello-femoral joint have been taken into consideration are now giving excellent results. 5,6.

Isolated patello-femoral arthroplasties have been available for some years but little attention has been paid to the congruity of the patello-femoral

joint and the tracking of the patella. Reasonable results can be obtained from the earlier designs, but they tend to deteriorate with time and do

not approach those of the total joint replacement. 7,8,9,10,11,12,13,14,15,16

The Avon™ Patello-Femoral Joint Arthoplasty is designed to reproduce accurately the congruity of the natural patello-femoral joint throughout

its range of movement and to facilitate central tracking of the patella in the trochlear groove.The trochlear surface is broad proximally to allow

free movement of the patella in extension.The femoral component can be translated laterally and placed in 3-6º of external rotation to reduce

lateral overload.The trochlear funnels to capture the patella as flexion occurs facilitating central tracking. Contact of the patella with the trochlear

is maintained up to 100º. 5,6,17,18,19

IndicationsPatients who have isolated patello-femoral arthritis with intrusive symptoms which have not been controlled by conservative management, can

obtain good results from this procedure. Radiological screening with a weight bearing antero-posterior and weight bearing lateral view with a

tangential patello-femoral view at 30º of flexion (Merchant’s view) can identify patients eligible for the procedure.

The arthritic disease should be confined to the patello-femoral joint with a substantially normal tibio-femoral joint.The final decision however

has to be made at the time of arthrotomy. Small areas of local chondral damage on the medial or lateral femoral condyles of the tibio-femoral

joint are acceptable, and may be treated by a local chondrectomy. It is essential that the menisci and cruciates are intact and that there is a good

range of movement in the joint. Like all arthroplasties, success depends on selection criteria, a technically competent procedure and carefully

controlled rehabilitation.

1

The Avon™ Patello-femoral ArthroplastyDesigned and developed by Mr Christopher E.Ackroyd FRCS,Avon Orthopaedic Centre, Bristol, UK


2

References1 McAlindon TE., Snow S., Cooper C., Dieppe PA. Radiographic pattern of osteo-arthritis of the knee joint in the community:

The importance of the Patello-femoral joint. Annals of Rheumatic Diseases. 1992; 51: 844-8492 Davies AP.,Vince AS., Shepstone L., Donell ST., Glasgow MM. The Radiologic prevalence of patello-femoral osteoarthritis. Clin

Orthop 2002; 402: 206-212.3 Noble J., Hamblen DL. The Pathology of the degenerate meniscus lesion. J Bone Joint Surg (Br) 1975; 57-B: 180-186.4 Ackroyd CE., Polyzoides AJ. Patellectomy for Osteoarthritis. A study of 81 patients followed for 2 to 22 years.

J Bone Joint Surg (Br) 1978; 60-B: 353-7.5 Black DL., Cannon SR., Hilton A., Bankes MJK., Briggs TWR. The Kinemax Total Knee Arthroplasty.

J Bone Joint Surg (Br) 2001; 83-B: 359-363.6 Harwin SF. Patello-femoral complications in symmetrical Total Knee Arthroplasty. J Arthroplasty. 1998; 13: 153-162.7 McKeever DC. Patellar prosthesis. J Bone Joint Surg (Am) 1955; 37-A: 1074-1084. page 136, paper 711.8 Arcerio RA., Major MC.,Toomy HE. Patello-femoral arthroplasty: a three to nine year follow-up study. Clin Othop 1996; 330: 130-151.9 Argenson J-NA.,Guillaume J-M.,Aubaniac J-M. Is there a place for patello-femoral arthroplasty? Clin Orhtop 1995; 321: 162-167.10 Cartier P., Sanouiller JL., Grelsamer R. Patello-femoral arthroplasty: 2-12 year follow-up study. J Arthroplasty. 1990; 5: 49-55.11 Krajca-Radcliffe JB., Coker TP. Patello-femoral arthroplasty: a 2 to 18 year follow-up study. Clin Orthop 1996; 330: 145-151.12 Lubinus HH. Patella glide bearing total replacement. Orthopaedics 1979; 2: 119-127.13 Smith AM., Peckett WRC., Butler-Manuel PA.,Venu KM., d`Arcy JC. Treatment of patello-femoral arthritis using the Lubinus

patello-femoral arthroplasty: A retrospective review. The Knee 2002; 9: 27-30.14 Tauro B.,Ackroyd CE., Newman JH., Shah NA. The Lubinus patello-femoral arthoplasty. J Bone Joint Surg (Br) 2001; 83-B: 696-701.15 Witvoet J., Benslama R., Orengo P, et al. Guepar femoropatellar prosthesis: description: initial results. Rev Chir Orthop Reparatice

Appar Mot 1983; 69 (Suppl II): 156-158.16 Witvoet J. Etat Actuel des Prostheses Femoro-patellaires. In Chasiers d`enseignement de la Sofcot. Expansion scintifique Francaise.

1994; 46: 79-92.17 Goodfellow J., Hungerford DS., Zindel M. Patello-femoral joint mechanics and pathology. J Bone Joint Surg (Br) 1976; 58-B: 287-290.18 Ackroyd C.E., Newman J.H. The Avon Patello-Femoral Arthroplasty - Development and early results.

J Bone Joint Surg (Br) 2001; 83-B: Sup. II 146.19 Ackroyd CE., Newman JH. The Avon Patello-femoral Arthroplasty - Two to five year results. J Bone Joint Surg (Br) 2003; 85-B Sup:

In press.20 Bach CM., Steingruber IE., Nogler M., Orgon M.,Wimmer C., Göbel G., Krismer M. Scoring Systems in Total Knee

Arthroplasty. Clin Orthop 2002; 399: 184-196.21 Feller JA., Bartlett RJ., Lang DM. Patellar Resurfacing versus retention in Total Knee Arthroplasty. J Bone Joint Surg (Br) 1996; 78-B:

226-8.22 Dawson J., Fitzpatrick R., Murray D., Carr A. Questionnaire on the perceptions of patients about Total Knee replacement.

J Bone Joint Surg (Br) 1998; 80-B: 63-9.

Pre-OpTypical pre-operative X-ray of a patient with severeosteo-arthritis of the patello-femoral joint.

Post-OpSame patient post-operative X-ray at one year.

Avon™ Surgical Technique

Post-Operative InstructionsPost-operative rehabilitation is similar to cases undergoing total knee replacement. Surgeons will notice that rehabilitation is considerably faster

than with a total knee replacement. Suction drains, if used, should be removed within 20 hours. Ice and anti-inflammatory analgesics should be

used regularly to reduce pain and swelling for at least two to three weeks. If flexion is slow to develop within two to three days then continuous

passive motion can be helpful.

The patients are generally able to get up and walk on the first post-operative day and start an active range of knee movement. Ninety degrees

of knee movement is generally achieved within 4-6 days and the patients can be discharged within this period.

Occasionally patients are slow to mobilise in which case more intensive rehabilitation is required. If there is a significant haemarthrosis then an

early arthroscopic wash out is advised. If more than 90 degrees of movement has not been obtained within four weeks then admission for

manipulation and intensive rehabilitation is essential.


Surgical TechniqueThe patient is prepared for total knee replacement surgery.A leg holder or sandbag and pillar allow support of the legfor easy adjustment. A tourniquet is generally used.A medial parapatellar incision is preferred.

• Step 1

• Step 2

The incision is made with the knee flexed to 90 degrees.It should be extended to the tibial tubercle and the capsuleincised on the medial side. Care should be taken not todamage the medial meniscus during division of the synovium.The lateral flap should be released to enable the fat pad andthe patella to be everted, dividing the inferior plica fold andthe lateral femoral fold, close to the femur to avoid damageto lateral geniculate vessels. Be careful to avoid damage tothe anterior meniscal and cruciate structures.

The patella is everted laterally to expose the anterior aspectof the knee joint. The synovium around the edge of thepatella is incised to define the edges. Release of the lateralretinaculum from the lateral margin of the patella andosteophyte is always required. (A peri-patella release).

A notchplasty may be required to remove notchosteophytes, confirming the integrity of the cruciateligaments.

The index finger is inserted into the notch to ensure asmooth arch and adequate space for the cruciate ligaments.

The anterior aspect of the femur should be exposed byincision of the anterior synovium of the supra patella pouch.The flaps are elevated to get a good view of the anteriorcortex of the femur.

• Step 3

• Step 4

3

1

2

3

4


• Step 5

• Step 6

• Step 7

Place the anterior cutting guide onto the femoral condylesso that the flat surface is parallel to the anterior cortex ofthe femur.This is facilitated by the saddle of the guide whichis placed in the notch of the femur. The two inferior skidsprovide a reference for placement against the posterioraspect of the condyles, although this cannot be seen easilywith the limited incision that is generally used.

The extra medullary guide rod and tower assist in obtainingaccurate alignment.This should be in line with the anteriorcortex of the femur in the lateral saggital plane. A 3.2mmdiameter hole is drilled into the intramedullary canalthrough the central drill guide of the cutting block and theGuide Rod inserted.

Final positioning of the femoral cutting block is confirmedwith respect to rotation. Particular attention should bemade to ensuring that there is 3-6º of external rotation ofthe block on the femur. Internal rotation will lead to maltracking and overload and should be avoided. Whensatisfactory alignment has been achieved the position of the

block is fixed with two 3.2mmdiameter pins. The lateral pinshould be inserted first toprevent internal rotation of theblock.The extra medullary toweris now unscrewed.

4

5

6

7

The height of the trochlea is assessed using the anteriorreference indicator which measures the exit point of theanterior resection using the superior surface of the cuttingblock.The cut should pass just beneath the deepest part ofthe groove, exiting parallel to the anterior cortex.

• Step 8

8


3-6ºExternalRotation

TranscondylarAxis

Lat Med

6430-1-001

Avon AnteriorCutting Guide

6430-1-450

Extra Medullary FemoralAlignment Rod

6430-1-400

Femoral AlignmentGuide

5800-4-1251⁄8" Diameter Drill

6430-1-010

AvonIntramedullary Rod

6784-8-1451⁄8" Diameter Pins

6633-8-052Anterior Reference

Indicator


• Step 9

If the zero position of the cutting guide produces a resectionwhich removes too much bone, then the 2mm,4mm or 6mmplates may be added to raise the level of the cut so thatnotching of the anterior femoral cortex does not occur. If indoubt always use a thicker cutting plate to remove theminimum amount of bone, more can be removed later ifrequired.

Once a satisfactory resection of the anterior trochlea hasbeen achieved, place the Trial Template onto the cut bonesurface. Sizing is correct when a gap of 2mm is presentbetween the template and the anterior part of theintercondylar notch. This will allow a thin bridge of intactarticular cartilage between the intercondylar notch and theposterior edge of the prosthesis. The articular cartilage atthe edge of the template is marked with a pen. (See Step12b).

• Step 10

5

9

10

11

• Step 11

The articular cartilage underlying the area of the template isremoved so that the prosthesis can be inset close to thearticular edge. This can be lifted off the sub-condylar boneusing a 10mm osteotome held in bold hands and movedvertically across the surface. A 5mm osteotome is used tocomplete the removal at the tip of the prosthesis.

The bone is then shaped to provide a smooth transitionbetween the anterior surface of the femur and the curvedpart of the condyles.This is easily done with the edge of theoscillating saw, osteotome or a bur.This is checked with thetemplate.

12

• Step 12a

6430-1-002 2mm Plate6430-1-003 4mm Plate6430-1-008 6mm Plate

Anterior Cutting Guide

6430-1-100 - SM6430-1-200 - MED6430-1-300 - LGE

Avon Drill Templates

6430-1-009

Avon 4.5mm Drill

6633-7-605

Pin Puller

6430-1-101 - SM6430-1-201 - MED6430-1-301 - LGE

Avon Femoral Trials

6430-1-006

Femoral Impactor

6784-8-1451⁄8" Diameter Pin


• Step 12b

• Step 13

• Step 14a

The four guide holes in the template are drilled with the4.5mm drill to accommodate the fixation studs of theimplant. The template is then removed and the trialprosthesis impacted into position to provide a correct fit.The inferior stud of the femoral component is inserted first.The prosthesis is punched into position in the line of thelong axis of the femur. The angle is then increased to 30º,then to 70º and finally to 90º with the second flat surface ofthe punch.

The Patella.The soft tissue attachments at the periphery of the patellaare incised to expose the insertions of the quadriceps andpatella tendons. The lateral patello-femoral synovial fold isincised and released close to the femur avoiding thegeniculate arteries. An important release of the lateralretinaculum is performed on the lateral margin of the patellafrom the proximal quadriceps tendon down to the distalpatella tendon. Sufficient release should be performed sothat the patella moves freely both medially and laterally.(A sub-periosteal Peri-patella release).

The height of the patella is measured with the callipers.(Measurement A). Allowance is made for the patella wear.Thepatella cutting guide is positioned so that after allowing forthe worn bone and cartilage, between 6mm and 11mm isremoved.This is equivalent to the thickness of the prosthesisand should correct restoration of patellar height. A minimumof 12mm of patella bone should always be left after theresection.

6

13


• Step 14b

14

Once a perfect fit of the template has been achieved, thefemoral template is punched into position and secured usingfour pins.

6633-7-855

Patella Caliper

6633-7-736

Patella Resection Guide

6633-7-744

Patella Clamp

6776-8-945

Patella TemplateAttachment

6776-8-901 - SM/LGE6776-8-903 - MED

Patella Drilling Templates

6776-8-909

Patella Drill

6633-7-738

Patella Stylus

6430-1-020 - SM6430-1-030 - MED6430-1-040 - LGE

Avon Patella Trials


The patella is reduced and the tracking checked to assessstability of the patella in the femoral groove while the kneeis flexed through 120 degrees.The medial facet of the patellashould be in contact with the femur throughout the range ofmovement.The ‘rule of no thumb’ is applied by ensuring thattracking is stable without pressure from the thumb. Iftracking is not perfect further release of the retinaculumfrom the edge of the patella should be performed.The stitchtest helps to judge the patella tracking. If there is persistentmal-alignment of the patella then it may be necessary toconsider bony or soft tissue realignment using the Roux orElmslie techniques. If this is felt to be inadvisable then thesurgeon should proceed to a total joint replacement whichwill allow correction of tibial rotation.

• Step 16

• Step 17

Once satisfactory tracking has been confirmed, bone cementis applied to the cut anterior femoral surface and the patella,using a cement gun (with an oblique cut to the nozzle) topressurise the cement.

The Femoral Impactor and Patella Clamp are used to seat thefemoral and patellar prosthesis. The inferior stud of thefemoral component is inserted first. The prosthesis ispunched into position in the line of the long axis of the femur.The angle is then increased to 30º, then to 70º and finally to90º with the second flat surface of the punch. A final checkof satisfactory patella tracking is made and the wound isclosed in the usual way.

Ensure there is no edge impingement of the medial borderof the patella on the femoral condyle at 120º flexion.The flatodd facet of the button should present a smooth surface atthis point.

7

15

• Step 15a

An oscillating saw is used to make the cut and the residualbone thickness checked with the Callipers (Measurement B,Step 14b).

• Step 15b

16

17

Apply and centralise the Patella Drill Template and drill thethree peg holes. The appropriate patella trial is inserted(small, medium, large) and the restored height is checked(Measurement C, Step 14b). The thickness of the patellaprostheses are: Small 9mm, Medium 9.5mm and Large10mm.

6430-1-006

Femoral Impactor

6430-0-100 - SM6430-0-200 - MED6430-0-300 - LGE

Femoral Prosthesis

6430-0-020 - SM6430-0-030 - MED6430-0-040 - LGE

Patella Prosthesis

6633-7-744

Patella Clamp

6633-7-746

Clamp Attachment


8

Factors that Facilitate Accurate Patella Tracking

1 Design of Femur and Patellaa. Shape of the trochlea allows unconstrained movement in extension.The patella is then captured by the

groove as the knee flexes to 90º.b. The patella dome has 3mm medial offset.

2 Position of Femur and Patellaa. Femoral component positioned in slight external rotation (maximum 6º).b. Femoral component positioned slightly lateral (1-2mm) to the intercondylar mid-line.c. Anterior cut parallel to the anterior femoral cortex to avoid elevating the trochlear.d. Patella measured prior to resection to ensure approximate reconstruction of the original patella thickness.e. Patella jig positioned so patella resection is symmetrical.f. Residual patella bone thickness of 12-15mm to avoid overstuffing of the joint.

3 Soft Tissue Releasesa. Release the lateral patello-femoral fold close to the femur.b. Lateral retinaculum dissected off the lateral osteophyte of the patella to release the lateral retinacular

contracture. (A sub-periosteal Peri-patella release).c. At full extension, flip the replaced patella at 90º to the trochlear.The retinaculum should be loose enough to

allow the edge of the patella to reach medial to the mid-line of the trochlear grove. (Flip test).

4 Assessment of Trackinga. The medial patella facet should remain in contact with the medial trochlear and femoral condyle throughout

the full range of motion.The patella odd facet will bear against the medial femoral condyle in deep flexion (over 110º). Ensure there is no impingement as the patella rotates internally at 120º of flexion.

b. If any tendency is observed for the medial facet to lift from the femoral trochlear, then a further release ofthe lateral retinaculum from the border of the patella should be performed. A mid lateral release is avoidedto prevent damage to the lateral retinacular vessels and soft tissue haematoma. (This considerably slowsrecovery).

c. If tracking is not perfect, then a single stitch can be applied to the mid-point of the retinaculum and thetracking reassessed.This simulates wound closure. (Stitch test).

d. If lateral mal-alignment persists then consider tibial tubercular reposition or revert to a total knee placement.


Case History

A/P

Post-OpSame patient post-operative X-ray

Pre-OpTypical pre-operative X-ray of a patient with severe osteo-arthritis of the patello-femoral joint

Lateral Tangential 30º

A/P Lateral Tangential 30º


9

Clinical ResultsThe Avon™ Patella has now been available for over six years, since September 1996.The results to date have shown that for the appropriate

indications there is considerable improvement in pain and function as assessed by pain scores, Bartlett score and Oxford function scores.

The results at 2 and 5 years are similar to those obtained for total knee replacement.

At 5 years the results to date show that very good function has been maintained.There have been very few complications attributable to the

arthroplasty and no cases of deep infection, patella fracture, wear or loosening. Disease progression in the tibio-femoral joint has occurred in a

small number of cases. Results suggest this can occur in about 7% of cases. For those with medial progression, a unicompartmental arthroplasty

can be inserted, provided the A.C.L is intact and the lateral compartment is in perfect condition. Alternatively proceed to revision with a Stryker®

total knee system.

The following 2-5 year results have been presented to BOA in September 2002. 18,19

Oxford Knee Score 22

(12 Questions. Range 0 - 48. Normal Knee = 48)

Bartlett Patella Score (30) 21Bristol Movement Score (20 = 120º) 18,19

Bristol Pain Score (40) 20

• Pre op: 207 Knees. Score: 15.0• 8 months: 120 Knees. Score: 35.0• 2-5 years: 95 Knees. Score: 35.0

• Pre op: 207 Knees. Score: 114º• 8 months: 120 Knees. Score: 120º• 2-5 years: 95 Knees. Score: 120º

• Pre op: 207 Knees. Score: 19.0• 8 months: 120 Knees. Score: 37.0• 2 years: 95 Knees. Score: 40.0

• Pre op: 207 Knees. Score: 10.0• 8 months: 120 Knees. Score: 25.0• 2 years: 95 Knees. Score: 26.0

Pain Score

Movement Score Bartlett

Oxford Knee Score

Pre-op

8 mths 2-5 yrs

Pre-op

8 mths 2-5 yrs

Pre-op

8 mths2-5 yrs

Pre-op

8 mths 2-5 yrs


Preparation and Trial Trays

10


Avon™ Patella Instrument Tray

Patella Instrument Tray

6430-2-200

6430-2-100


Order Codes

Avon™ Instruments6430-1-001 Avon™ Anterior Cutting Guide6430-1-002 Avon™ Anterior Cut Guide - 2mm Plate6430-1-003 Avon™ Anterior Cut Guide - 4mm Plate6430-1-008 Avon™ Anterior Cut Guide - 6mm Plate6430-1-400 Femoral Alignment Guide6430-1-450 Femoral Long Alignment Rod6784-8-145 Kx Mod 1/8” Pins5800-4-125 Gray Bone Drill 1/8” (3.2mm) x 4” Long6430-1-020 Avon™ Patella Trial SMALL

6430-1-030 Avon™ Patella Trial MEDIUM

6430-1-040 Avon™ Patella Trial LARGE

6430-1-006 Femoral Impactor6430-1-009 Avon™ 4.5mm Drill6430-1-010 Avon™ Long Alignment/Intramedullary Rod6430-1-100 Avon™ Drill Template SMALL

6430-1-200 Avon™ Drill Template MEDIUM

6430-1-300 Avon™ Drill Template LARGE

6633-7-605 Pin Puller

6430-1-101 Avon™ Femoral Trial SMALL

6430-1-201 Avon™ Femoral Trial MEDIUM

6430-1-301 Avon™ Femoral Trial LARGE

Patella Instruments6776-8-901 Kx Patella Drilling Template SMALL

6776-8-903 Kx Patella Drilling Template MEDIUM

6776-8-945 Kx Patella Template Attachment6776-8-909 Kx Patella Drill with Stop6633-7-736 Kx Patella Resection Guide II6633-7-744 Monogram Patella Clamp6633-7-746 Clamp Attachment6633-7-738 Monogram Patella Resection stylus Guide6633-7-855 Monogram Patella Caliper6633-8-052 Anterior Reference Indicator

Trays6430-2-100 Kx Patella Instrument Tray (Empty)6430-2-200 Avon™ Patella Instrument Tray (Empty)

Avon™ Components6430-0-020 Avon™ Patella Component SMALL

6430-0-100 Avon™Femoral Component SMALL

6430-0-030 Avon™ Patella Component MEDIUM

6430-0-200 Avon™Femoral Component MEDIUM

6430-0-040 Avon™ Patella Component LARGE

6430-0-300 Avon™Femoral Component LARGE

Reorder code: 64301452LI - Rev2 08/03

www.avonpatella.com

For more information, contact your local Stryker Howmedica OsteonicsSales Representative, or visit our website at;

Raheen Business ParkLimerickIreland

TEL: +353 61498200FAX: +353 61498281


Documents

New Avon Surgical Technique.qxd 8/5/03 12:14 PM Page 2 · Introduction Isolated patello-femoral arthritis occurs in up to 10% of patients with arthritic symptoms in the knee joint.1,2,3